Modeling vs Sculpting when to use?
While as Luke mentions this is mostly an opinion based question, subject to personal preference, and largely dependent on what you are trying to achieve, I'll only add that while I see as sculpting a good starting point for planning the base shape of a model or as a finalizing step to add fine details over it, I find that in most situations it is often not a good "final product" on its own.

Sculpting will frequently produce triangulated output and messy meshes especially if using Dynamic Topology-like features. This results in poor topology that is largely unsuitable for the most common tasks that follow to produce a proper final product, like UV Mapping, rigging, armatures, making it hard to animate, tweak or texture.

This will not yield a pleasant model to work with, easy to edit or alter, as such I see sculpting more as a starting point then a final result.

If you plan to unwrap or UV map your model, animate, use modifiers, optimize your mesh or do anything involving exporting elsewhere (like game engines) you will eventually need a good base model, hand modeled with intent and proper quad dominant high quality topology.